1. Field of the Invention
This invention relates to a fluid flow nozzle, in particular to a filling nozzle of a machine for filling containers with liquid.
2. Description of the Prior Art
In the manufacture of certain types of non-returnable packages for dairy products, the packaging containers are filled with the help of metering pumps. Such pumps at each pumping stroke meter out the desired amount of liquid to a chamber whence the liquid is transferred to the container to be filled.
In order to prevent after-dripping between pumping strokes, it is known from British Patent Specification No. 2095584 for a filler to include a non-return valve and a flexible nozzle having a cruciform slit which is normally urged closed by the flexibility of the material. The non-return valve, with the aid of a piston component thereof, after the completed pumping stroke, creates a suction on the liquid in the nozzle, so that the nozzle is closed more rapidly and effectively than it would be if its closing were to rely simply upon the flexibility of its material. The cruciform slit of this flexible nozzle gives a number of disadvantages. Firstly, it does not reliably seal, particularly at its centre. Secondly, in the open condition of the nozzle, the lips of the outlet mouth of the nozzle adopt a zig-zag form as viewed perpendicularly to the axis of the nozzle, so that, in filling the bottom of a carton, foaming and splashing can occur owing to the tops of the zig-zags being above the liquid level, and, in filling the remainder of the carton, either this foaming or splashing continues to occur, or the nozzle has to be dipped to a sufficient extent into the liquid to ensure that all of each zig-zag is below the surface of the liquid.
A liquid dispensing container having a flexible nozzle is disclosed in U.S. Pat. No. 4,139,124. The container consists of a cup and a cover. The cup contains the liquid, whilst the cover is provided with a pressure controlled flexible nozzle which is opened and closed by applying and releasing pressure on a resiliently flexible wall part of the cover opposite the flexible nozzle. An increase of pressure within the container by pressure on the flexible wall part causes automatic opening of the flexible nozzle, whilst a decrease of pressure in the container causes the nozzle to close. A collection spout surrounds the flexible nozzle and any dripping of liquid occurring when the contents of the container are being dispensed is collected in the spout and forced back into the container through a valve-controlled orifice when pressure on the flexible wall part is released. The specification discloses various forms of nozzle mouth in its closed condition. Among these are a curciform slit and a slit which is linear with forked ends. The resilient walls of the nozzle are provided with resilient beads which are integrally joined at one end to the cover and which lie on the outside of the resilient sheet material of the nozzle whilst extending along the nozzle. This nozzle is not designed to contain liquid continually and for that reason liquid-tight sealing at the mouth of the nozzle in the closed condition is not vital, as it is with a carton filling machine. In practice, the use of the beads within folds of the resilient nozzle material makes it difficult to obtain liquid-tight sealing.
Particularly on high-speed fillers, it is important to minimize the problems of splashing and foaming on injection.